What is Code Coverage?
Code Coverage is a metric that determines the extent to which the source code of your application is executed when the application is run. It’s a crucial aspect of software testing that helps in identifying untested parts of a code. It helps developers ensure that the quality of the software remains high by detecting areas of a code not covered by a test and prompting for additional testing to be carried out.
Importance of Code Coverage
- Code Quality: Code coverage helps to maintain high code quality by ensuring all parts of the code are tested and work as expected.
- Identify Untested Code: It helps in identifying areas of a code not covered by a test, therefore, prompting for more testing to be carried out.
- Reduce Bugs: By ensuring that each part of the code is tested, code coverage can help reduce the number of bugs that make it to production.
- Improve Design: If a part of the code is difficult to test, it might suggest that the design of your code needs to be improved.
Measuring Code Coverage
Code coverage is usually expressed as a percentage and calculated as the number of lines of code executed by testing divided by the total number of lines of code. Here are few types of code coverage:
- Function Coverage: Measures whether each function or subroutine in the code base has been called.
- Statement Coverage: Measures the number of statements that have been executed in the software.
- Branch Coverage: Measures the number of branches (from decision points) that have been executed.
- Condition Coverage: Measures the boolean sub-expressions in decision instructions that have been evaluated to both true and false.
Code Coverage Tools
There are various tools available that can help measure code coverage. Some of them include:
- Jacoco: A free code coverage library for Java.
- Cobertura: A free code coverage tool for Java.
- Codecov: Provides highly integrated tools to group, merge, archive and compare coverage reports.
While code coverage is a valuable metric, it should not be the only measure of the quality of your tests. It is possible to have high code coverage and still have bugs slip through. Therefore, it is important to also consider other testing metrics and methodologies in your software testing strategy.